1. Field of the Invention
An endodontic reamer and method for manufacturing endodontic reamers and files, more specifically a novel endodontic reamer comprised a longitudinal shaft having projecting wedges, and a novel method of forming an endodontic instrument with compression.
2. Background Information
The field of endodontics involves diseases of the tooth pulp, commonly known as a root canal, and typically requires the dentist to remove infected material from within the pulp of the tooth. The root canal itself is the space within the tooth that carries the blood supply into the tooth and contains the pulp. Within the root canal the pulp contains the nerve endings, which causes pain to warn when one bites down too hard on a hard object. From time to time, this space (the root canal) becomes infected and requires the dentist to clean (ream) out the root canal space in order to remove the pulp and/or other infected material. This cleaning consists of using a series of instruments to remove the pulp and infected material by enlarging and conically shaping the canal. Once cleaned and shaped, the space is sealed so that it does not become reinfected once again. It is the dentist's goal to provide complete cleaning by removing as much of the infected material as possible. The more infected material that is removed, the more likely the case has of being successful and thus the tooth saved. Otherwise, the tooth must be extracted and the space filled with a false tooth or treated by other means.
Endodontic reamers typically have helically wound cutting edges (blades). Rotation of the reamer allows the cutting blades to work within the root canal to cut dentin and remove infected material from the walls of the canal. Applicant has invented a novel endodontic reamer for effective cutting and removing of material that overcomes many limitations of the prior art of helically wound reamers. Applicant's novel endodontic reamer is comprised of a shaft having a longitudinal axis and wedge sections, not helically wound, with respect to the longitudinal axis.
Applicant provides a novel reamer for engagement at first end with a handle for manual manipulation or powered by a dental handpiece and a second end for engagement within the root canal of a patient requiring root canal therapy. Typically, the wedges are wider than the diameter of the shaft. Furthermore, the shaft is typically flexible as opposed to being rigid. This flexibility helps allow the reamer to stay centered within the root canal. The Applicant's wedges include forward and trailing portions that are typically at an angle oblique to the longitudinal axis. One or more cutting edges, which in a preferred embodiment may be straight, are typically provided—radiating outward around the shaft. A novel pilot tip guides the flexible shaft within the canal. The pilot tip can be cutting or noncutting.
The novel endodontic reamer's cutting blades can be typically very narrow and sharp; increasing it's cutting efficiency and reducing the number of instruments required by the dentist for treatment. Reducing the number of instruments also reduces the treatment time for both the dentist and patient. The cutting blades are typically made very thin, thus reducing the surface area contact of the blade with the root canal walls. These thin blades (typically from 0.01 mm to 1.00 mm thick and preferably from 0.05 mm to 0.25 mm thick) also allow for more space for the previously cut material to reside before being irrigated and suctioned from the canal. When compared to prior art, this extra space helps reduce the loss of cutting efficiency that the cut material often causes by interfering with the cutting action of the blades. Thin blades increase cutting efficiency and reduce torsional stress on the shaft. Stress by torsion (twisting along the long axis of the shaft) is a primary cause of premature instrument breakage.
Applicant's reamer is manufactured by a novel method. This method includes using wire of the same diameter as the shaft of the finished product. The wire form may be cylindrical or tapered and be made from nonmetal or metals such as nitinol, stainless steel, and carbide steel. The wire provides the “blank” for the reamer. A second end of the wire, near the cutting portion is located and then swaged, coined, hot or cold formed, forged, pressed or otherwise subjected to mechanical compression to “flare” the second end such that it is flattened—thereby, having a width greater than the unflattened (round portion) of the wire and having a thickness narrower than the round portion in the other dimension. The leading edge of the flattened portion may be polished, machined, sheared or further formed into a sharp cutting edge.
In prior art, endodontic reamers have been ground into the desired shape. This grinding process is time consuming, requires many procedural steps and requires the use of very specialized, expensive machinery. This grinding process also generates imperfections and flawing on the surface of the finished work piece. These imperfections and flaws on the reamer's surface may lead to premature failure, increasing the risk to the patient, reducing the reamer's useful life and causing it to be more expensive for the dentist to use. This cost is thus passed onto the patient in the form of higher treatment costs. Thus for economic, rather than biological reasons, teeth are being unnecessarily extracted rather than saved.
Applicant's also provide for a novel process of manufacturing a dental instrument, including the novel reamer. Because the novel shaft is made without grinding the outside surface down to the desired the diameter, typical of prior art, less material is removed (wasted) and less material must be handled for disposal. Of significant importance, the surface of the shaft is not marred through the grinding process. The instrument's fatigue life is extended because the surface of the shaft is kept in its original state as when drawn into wire form. Finally, this simplified forming process allows for less complex and less expensive equipment to be used for manufacturing. The time to manufacture such an instrument is reduced. Less specialized equipment and the elimination of the time required to grind down the shaft reduces the cost of manufacturing such reamer.
Applicants also provide a novel handle, the handle for holding a file or reamer. Applicants' novel handle may include a shank. The shank is cylindrical and is designed to engage a file or a reamer. Applicants' novel handle includes a portion, typically along the shank, having a reduced diameter. This reduced diameter may take the shape of a groove (U-shaped) or a notch (V-shaped). By providing such a reduced diameter, Applicants provide a predictable break point, such that a file or reamer does not break in the tooth, but at the break point at the reduced diameter. In other words, rather than having a file or reamer break along a shaft or other part thereof, and thus be difficult to retrieve, Applicants' novel handle with a reduced diameter will break first and, will be far easier to retrieve from the tooth than a piece of a file or reamer that may be deep within the canal of the tooth.